The present invention relates generally to herbicidal compositions or formulations, and to methods of using such compositions to kill, or control the growth and proliferation of, unwanted plants. In particular, the present invention relates to herbicidal compositions, as well as their methods of use, which comprise N-phosphonomethylglycine, or a herbicidal derivative thereof, and a pyridine analog, or a herbicidal derivative thereof, optionally with one or more suitable surfactants. Such compositions cause early visual symptoms of treatment and/or enhanced effectiveness or control when applied to the foliage of plants.
Herbicidal compositions comprising the herbicide N-phosphonomethylglycine or derivatives thereof (“glyphosate”), are useful for suppressing the growth of, or killing, unwanted plants such as grasses, weeds and the like. Glyphosate typically is applied to the foliage of the target plant. After application the glyphosate is absorbed by the foliar tissue of the plant and translocated throughout the plant. Glyphosate noncompetitively blocks an important biochemical pathway which is common to virtually all plants, but which is absent in animals. Although glyphosate is very effective in killing or controlling the growth of unwanted plants, the uptake (i.e., absorption) of glyphosate by the plant foliar tissue and translocation of glyphosate throughout the plant is relatively slow. Visual symptoms that a plant has been treated with glyphosate may not appear until one week or more after treatment.
Compositions comprising glyphosate may be formulated with one or more surfactants to enhance their effectiveness for foliar application. When water is added to a composition formulated with surfactants, the resulting sprayable composition more easily and effectively covers the foliage (e.g., the leaves or other photosynthesizing organs) of plants. Glyphosate salts, for example, have been formulated with surfactants such as polyoxyalkylene-type surfactants including, among other surfactants, polyoxyalkylene alkylamines. Commercial formulations of glyphosate herbicide marketed under the trademark ROUNDUP® have been formulated by Monsanto with such a polyoxyalkylene alkylamine, in particular a polyoxyethylene tallowamine.
As a result of the somewhat slow development of visual symptoms that may result when glyphosate is utilized alone, formulations or compositions containing glyphosate and another herbicide have been suggested, in an attempt to achieve both early visual symptoms of plant treatment and prolonged control of the plant. For example, some have suggested using a tank mix composition containing glyphosate and a contact herbicide, such as a pyridine analog like triclopyr (i.e., [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid) or a herbicidal derivative thereof. However, to-date, such tank mixes have generally (i) employed relatively low weight ratios of glyphosate to, for example, triclopyr (wherein glyphosate and triclopyr are present in equal amounts, glyphosate is in a slight excess, or triclopyr is in excess), and/or (ii) not utilized a surfactant therein.
For example, R. K. Howell et al. (Southern Weed Science Society Proceedings, 195-197 (1998)) disclose the preparation of a tank mixture containing a surfactant TL90, Roundup Pro® and Garlon™ 4, the glyphosate (in Roundup Pro®) and triclopyr (in Garlon™ 4) being present in an apparent weight ratio of approximately 1.3:1, respectively.
G. M. Wright et al. (North Central Weed Control Conference Proceedings, vol. 38, 139 (1983)) disclose the preparation of a tank mixture of glyphosate and triclopyr in the apparent absence of a surfactant, the glyphosate and triclopyr, respectively, being present in an apparent weight ratio of approximately 1.5:1.
M. L. McCormack et al. (Northeastern Weed Society Proceedings, vol. 36, 209-214 (1982)) disclose the preparation of a tank mixture of glyphosate and triclopyr in the apparent absence of a surfactant, the glyphosate and triclopyr, respectively, being present in an apparent weight ratio of approximately 1.4:1.
J. Lawrie et al. (Weed Research, vol. 33, 25-34, (1993) appear to disclose the preparation of a tank mixture of glyphosate, triclopyr and a surfactant-containing mixture, wherein the glyphosate and triclopyr, respectively, appear to be present in a weight ratio of approximately 1.67:1.
W. Harahap et al. (Biotrop Special Publication, no. 24, 317-24 (1986)) disclose the preparation of tank mixtures of glyphosate and triclopyr or picloram, in the apparent absence of a surfactant. In the tank mixtures, glyphosate and triclopyr are, respectively, present in an apparent weight ratio of approximately 9.5:1 or 11.5:1, while glyphosate and picloram are present in an apparent weight ratio of approximately 7.7:1.
S. H. Kay et al. (Southern Weed Science Society Proceedings, 291 (1992)) disclose the preparation of a tank mixture of glyphosate and triclopyr in the apparent absence of a surfactant, the glyphosate and triclopyr, respectively, being present in a weight ratio of approximately 1:1.
A Roundup Pro® Supplemental Label (for application in California using a helicopter, EPA Reg. No. 524-475, Monsanto Company (1996)), discloses the optional preparation of a tank mixture of Roundup Pro® and Garlon™ 4 in varying weight ratios of glyphosate and triclopyr, respectively, as well as varying concentrations related thereto.
Tank mixtures require the user to purchase and store each herbicide used in the mixture separately, until the actual preparation of such mixtures in the field. The user must also measure out varying amounts of each herbicide used in the mixture. Therefore, a pre-packaged mixture (i.e., a concentrate) which already contains the desired herbicides in a single container may be desirable in some instances. However, concentrates may be difficult to prepare, for example when one of the herbicides is not soluble or miscible with the same desired solvent (e.g., water).
The solubility or miscibility problems sometimes encountered with concentrates may be overcome by preparing a concentrated emulsion formulation. A concentrated emulsion formulation consists of two phases and is a dispersion of one immiscible liquid (i.e., the discontinuous phase) in a second liquid (i.e., the continuous phase). If the continuous phase is water, the emulsion is an oil-in-water type emulsion and the water-immiscible liquid or solution may be referred to as the “oil” phase (regardless of its composition). In a concentrated emulsion formulation, the active ingredient may be dissolved in an organic solvent along with added emulsifiers and/or dispersants. When the concentrate is added to water, the active ingredient becomes dispersed throughout the water. Such a concentrate, in the form of a microemulsion, was prepared in U.K. Patent Application No. GB 2 267 825 A, using a slight excess of the isopropylamine salt of glyphosate relative to the butoxyethyl ester of triclopyr (weight ratio of glyphosate to triclopyr approximately 1.6:1), and a high load or amount of triclopyr and two ethoxylated cocoamine surfactants, Ethomeen™ C-15 and C-25 (approximately 100 g/L triclopyr and approximately 285 g/L total surfactant).